As a tablet having a multilayer structure, tablets having a substantially columnar shape and layers in the columnar direction (center axis direction of the column) are known. This type of tablets is manufactured by compression molding from the columnar direction. These tablets are useful as tablets for combination medicament which hold a plurality of drugs in a single tablet, but there is a problem that the shape of the tablet is limited to columnar or the like due to limitation caused by the above-mentioned manufacturing method.
A tablet having such a structure can be used as a scored tablet of the same drug, but application is difficult in view of a difficulty in division caused by difficulty in giving a splitting groove or the limitation on the shape to a column.
As another tablet having a multilayer structure, a core tablet having a core inside the tablet is known, and this is useful as a tablet for combination medicament or a scored tablet, but there is also a problem such as constraint on a thickness of the tablet, complexity of a tableting machine and the like caused by necessity to insert the core. In manufacture of this type of tablets, compression from a different direction is not performed as disclosed in the International Publication No. WO03/026560.
As a special tablet having a multilayer structure, a tablet in which fractions of molded products are joined physically or chemically is disclosed in Japanese Patent Laid-Open Publication No. 6-9375. This can be used as a tablet for combination medicament or scored tablet, but there are problems that provision of a physical shape or addition of an adhesive layer for binding is required, a device and a process for binding are required and the like. And the molding is performed not by compression but by adhesion.
Compression is performed several times in tablet compression in many cases, but this is performed in the same direction, and its major purpose is to increase strength of the tablet after compression molding by expelling air existing between particles.
It is known in general that further compression to the primary compression molded product which might change its shape causes irreversible destruction of the molded product, and compression from a different direction is not carried out.
That is, manufacture of a tablet by performing compression molding again to a compression molded product containing those having a multilayer structure from a direction different from the compression direction has not been carried out and thus, a tablet compression machine for that purpose has not been known. Therefore, the tablets for combination medicament or scored tablets have their shapes limited, and manufacture thereof requires complicated devices and processes, which is a problem.